Abstract
Purpose: :
The retinal pigment epithelium is a primary target for cellular replacement in degenerative ocular diseases such as age related macular degeneration. Transplantation of cells to the subretinal space is typically achieved by injection of cell suspensions, however there are a number of disadvantages associated with this method, including cell death and incorrectly localised or disorganised grafts. Recent studies have demonstrated that growth of retinal cells on polymer scaffolds can facilitate the transplantation of cells, which may reduce cell death by up to 10 fold (1). There have only been limited investigations to determine the most appropriate polymer composition and conformation for optimal cell delivery.
Methods: :
Using a technique adapted from (2). We manufactured biodegradable microspheres using five different blends of poly(L-lactic acid) (PLLA) with poly(D, L-lactic-glycolic acid) (PLGA). Scanning electron microscopy (SEM) was used to characterise the microsphere size range produced and surface characteristics. Microsphere surface chemistry was modified using the extracellular matrix protein laminin. The microsphere blends were seeded with an ARPE-19 cell line and maintained in culture for up to 2 weeks. Cell adherence, proliferation and phenotype were assessed by immunocytochemistry using antisera directed against proliferating cell nuclear antigen, RPE65 and pan-cytokeratin. Cell survival was quantified by measurement of apoptosis and cell membrane integrity.
Results: :
Microsphere diameter and surface characteristics were dependent on the copolymer blend ratios and concentration of copolymer used. Attachment of ARPE-19 cells to coated and uncoated microsperes was confirmed. Cells proliferated, remained viable and retained phenotypic characteristics on all blends. There was a trends toward an increase in cell death on microspheres predominantely comprised of PLGA, however this may be attributed to the smaller size of these spheres leading to cell clumping, rather than a cytotoxic effect.
Conclusions: :
From this study we found microspheres to be an efficacious scaffold configuration for cell attachment and growth in vitro with preservation of phenotypic characteristics associated with minimal demonstrable cytotoxicity.(1) Tomita M et al. Stem Cells 2005 10:1579-88.(2) Gabler F et al. Biomolecular Engineering 2007 24: 515-520.
Keywords: transplantation • retinal pigment epithelium • age-related macular degeneration